Many electronic devices are tested for electrical and optical properties during manufacturing by automated test systems. Typical automatic test systems use precision electrical or optical test equipment to find values associated with electrical and optical properties of a device and either accept, reject or sort it into an output category depending upon the measured values. For miniature devices, automatic test systems are often designed to handle bulk loads, where the manufacturing process creates a volume of devices that have substantially identical mechanical characteristics such as size and shape but differ in electrical or optical characteristics. It is common practice to build a volume of devices with electrical and optical properties that generally fall within a range and rely on testing to sort the devices into commercially useful groups with similar characteristics.
These devices are often supplied to the test equipment as containers filled with devices. Typically the test equipment must extract a single device from the bulk load of devices, orient the device and fixture it so the test equipment can perform the desired tests. Testing often requires probing the device, wherein electrical leads are brought into contact with device to permit signals and power to be applied to the device and to monitor responses to the inputs. Other tests involve measuring light output from optical devices such as light emitting diodes (LEDs) in response to specific inputs. The task of the automatic test system is to determine the electrical or optical characteristics of devices and sort the devices into groups depending upon those characteristics.